Lasioglossum leucozonium

Lasioglossum leucozonium
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Hexapoda
Class:	Insecta
Order:	Hymenoptera
Family:	Halictidae
Subfamily:	Halictinae
Tribe:	Halictini
Genus:	Lasioglossum
Species:	L. leucozonium
Binomial name
Lasioglossum leucozonium Schrank, 1781

Lasioglossum leucozonium (Schrank, 1781), also known as Lasioglossum similis,^[1] is a widespread solitary sweat bee found in North America, Europe, Asia, and parts of northern Africa.^[2] While now a common bee in North America, population genetic analysis has shown that it is actually an invasive species in this region.^[3] This population was most likely founded by a single female bee.^[4]

L. leucozonium is part of the subfamily Halictinae, of the hymenopteran family Halictidae.^[5] The largest, most diverse and recently diverged of the four halictid subfamilies,^[6] Halictinae (sweat bees) is made up of five tribes of which L. leucozonium is part of Halictini, which contains over 2000 species.^[7] Genus Lasioglossum is informally divided into two series: the Lasioglossum series and the Hemihalictus.^[8] L. leucozonium is a part of the Old World series. It is most closely related to L. callizonium, L. zonulum, and L. majus. However, there is genetic variation within the species depending on its location.^[9]

While occasionally compared to its close relative, L. zonulum, L. leucozonium has distinct features that separate it from other Lasioglossum species. There are also differences in appearance between females and males.^[10] Additionally, its eye has been studied in relation to the nocturnal bee Megalopta genalis.^[11][12]

Female L. leucozonium are recognizable by their coarsely sculpted and relatively short propodeal dorsal areas.^[9] The smooth surface of these areas is strongly striate laterally to reticulate medially, which is a unique characteristic in the Eastern United States of the Lasioglossum species only shared by L. zonulum. Its dull, granulate first metasomal tergum has well-developed punctures separated by 1-1.5 times their width and its vertex behind the ocelli has conspicuous transverse striations. In comparison to L. zonulum, the pronotal angle of L. leucozonium is less strongly projecting but still obtuse. The pronotum has a well developed dorsal edge and an incomplete lateral ridge, of which the lower part is inconspicuous and broadly rounded, that is broadly interrupted by an oblique lateral sulcus. With a rounded mesoscutal lip that is strongly elevated from the pronotum, it has a propodeal triangle that is well defined by a carinate rim and a lateral carinae that becomes indistinct medially as it extends to the dorsal surface. It has an elongated head, a shiny face, an evenly rounded, weakly proturberant, and extremely granulate supraclypeal area that is uniformly and densely punctate with punctures separated by their width or less, and an obscurely granulated and shiny clypeus with a densely punctated surface that does not have a median longitudinal sulcation that projects below the lower margin of its eyes. The distance between its lateral ocelli is greater than that between the lateral ocelli and the eye. While the lateral edge of its metasomal tergum II is only faintly sinuate and virtually straight, the distal keel of its labrum is moderately broad from the front and gradually narrows moving back to the apex. Its moderately shiny mesoscutum has a microscopically patterned surface, and its scutellum is nearly uniformly punctate with punctures like that of the mesoscutum. There is white to yellowish white pubescence on the head and thorax, though the thorax has some brown hairs on the scutellum. The weakly differentiated hind tibial hair is mostly pale yellowish brown while the dorsal hairs are light brown. On the metasomal tergum I and terga II-IV, the hair is white with a band of hair on terga II-IV and elongate hairs scattered over the anterior surface of tergum I with no acaririarium. Its mesoscutal hairs are moderately dense and conspicuously plumose, and its wing membrane is hyaline.^[10]

A male L. leucozonium is distinguished by its rounded clypeus, its ventrally narrowed head, its yellow basitarsi of the middle and hind legs, its coarsely rugose propodeal dorsal surface, its dense, adpressed hair patch on the posterior edge of sternum V, and its inverted V-shaped patch of hair on sternum VI. In general, the males are similar to the females, however other differences include rounded gena wider than the eye; a broadly rounded clypeal surface; a labrum with rounded and weakly developed distal processes, a mostly evenly rounded basal area with small circular median depression, and weakly developed basal lateral depressions; and a short mandible. The shiny clypeus is weakly granuate, uniformly punctate throughout, with clypeal maculation. The foretarsi is entirely dark while the middle and hind basitarsi are yellowish white except for the dark distal edges. The hairs on sternum IV are erect and elongated without a noticeable pattern. Its sternum VII is somewhat reduced and slender, its sternum VIII does not have a median process, and its sternal disc is reduced and narrow. With respect to genitalia, the gonobase is moderately short with a gonostylus that is large, flat, and rounded apically. There is no retrorse membraous lobe, but there is volsella with prominent lateral flange.^[10]

As fast flyers, L. leucozonium uses compound eyes for orientation and foraging but only in bright light.^[13] Their eyes contain over 3,000 facets with a maximum diameter of 20 µm. With a 41-µm-thick cornea consisting of a convex inner and outer cornea, it has weakly developed and coalesced corneal protuberances.^[11] Its lamina has no branching and only its L2 and L4-fiber types are spread laterally.^[12]

L. leucozonium is found in open habitats, normally on sandy or chalky soil though it is also more rarely found on heavy clay.^[1] As a holarctic bee, it can be found from Wisconsin to New Jersey up to Cape Breton Island in North America as well as around Europe.^[10] Its nests can sometimes be found in aggregations, though it is a solitary bee.^[1]

Created by one to two females, the nest of L. leucozonium is made in flat to slightly inclined light soil in sparsely vegetated conditions or where there is a short expanse of short grass. Descending vertically, the main tunnel has cells at the end of short side tunnels. Nests can have 8 to 15 cells per female.^[1]

In North America, females and males are active around the same time; in general, they are most active between the beginning of May and mid-August.^[11] Females are most active in early June though they can be found from late May to October. Males are more active in late July and August but range from June to October.^[10]

L. leucozonium is only has a single generation per year.^[3] The cells of a nest fosters a sexual brood within the same year they are created. Once this brood matures in that year, they mate and then hibernate.^[1] While there is only a single generation in a year, it has two annual exits of female, one at the beginning where females make the nests and mate, and the other after the brood mates.^[14]

L. leucozonium is a diurnal,^[11] ground-nesting bee. During the wintertime, it hibernates, staying underground with females being singly-mated.^[3]

A mining bee, L. leucozonium digs into the ground to make its nests. One to two females help create the nest, and for each female, 8 to 15 cells are made. Since it is a solitary bee, most likely these females are working communally rather than socially. After the creation of the nest, the offspring mate and then the bees hibernate underground for the winter, most likely in different places from their original nests.^[1]

As a solitary bee, L. leucozonium generally works by itself. When another female works with it to build a nest, they work communally rather than socially,^[1] therefore they double the amount of work they can do rather than declining in efficiency with the added number of females.^[15]

L. leucozonium, though solitary,^[1] interacts with plants and parasites. Plants provide it with pollen and nectar as food for both themselves and their larvae, while parasites and predators affect their survival.^[1][10]

L. leucozonium adults and larvae feed on pollen from various flowers.^[1] As a generalist, it is not as picky about which flowers it chooses compared to a specialist.^[16] It also has been seen visiting apple trees and lowbush blueberries.^[17]

L. leucozonium most frequently visit yellow-flowered Asteraceae^[1] like Hieracium caespitosum, Krigia biflora, Rudbeckia hirta,^[18] but have been seen to also visit creeping thistle (Cirsium arvense)^[1] and other plants, which include plants from Campanula and Rosa^[10] as well as Cornus alternifolia.^[18] Males are also commonly found on Melilotus.^[10]

While there are no parasites of the genus Sphecodes that solely parasitize L. leucozonium, S. ephippius has been shown to parasitize it as well as other Lasioglossum.^[1]

A predator common to L. leucozonium is Philanthus wasps.^[10]

Even though L. leucozonium was an invasive species long ago,^[3] it has found its niche in nature and has been studied and utilized by humans.^[19][20]

The painful stings of bees are mostly associated with the poison gland and the Dufour's gland which are abdominal exocrine glands containing various chemicals. In L. leucozonium, the Dufour's Gland mostly contains octadecanolide as well as some eicosanolide. There is also evidence of n-triscosane, n-heptacosane,^[21] and 22-docosanolide.^[19] However, the secretions of these glands could also be used for nest construction as well.^[21]

L. leucozonium is an important pollinator due to its generalist nature.^[16] It has been shown to be important for the pollination of caneberry, though also shown as a pollinator for cucurbit, apple trees, and blueberry bushes.^[20]

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